1. Technical Field
The present invention relates to methods for adjusting ejection timing and ejection timing adjusting apparatuses.
2. Related Art
There are printers having two heads disposed lined up in a direction intersecting a row direction in which nozzles of nozzle rows are lined up. These two heads are disposed such that the position of one of the heads is shifted in the nozzle row direction by a distance corresponding to half a nozzle pitch. Through this, it is possible to double the resolution in the nozzle row direction. In order to perform printing using heads disposed in this manner, it is required to adjust in advance the landing positions of liquid droplets ejected from those two heads with respect to a transport direction.
A method has been used in order to adjust the landing position in the transport direction; an adjustment pattern, in which the ejection timings of liquid droplets ejected from a first head and a second head are shifted by small degrees, is printed, and then the optimal ejection timing of the liquid droplets is selected so as to carry out necessary adjustment (JP-A-10-329381).
However, when a roller for transporting paper is decentered or the like, the transport amount of paper varies when paper is transported. Then, such variance in the transport amount due to such decentering causes a transport error.
Forming an adjustment pattern and adjusting the ejection timing of liquid droplets based thereon results in adjustment of the ejection timing of liquid droplets based on the adjustment pattern formed while affected by a transport error. The transport error is composed of a consistent error component and an error component that periodically varies, the components being combined. It is difficult to determine the amount of the error component that periodically varies while the pattern is recorded. Therefore, it is impossible to properly adjust the ejection timing due to the indeterminable varying component contained in the transport error.